1. Field of the Invention
The present invention relates to a multiple port communication apparatus capable of accommodating a plurality of lines. More particularly, the invention relates to a communication apparatus capable of reducing power dissipation as much as possible in the state other than the operational state of the apparatus (such as being engaged in transmission and reception, or in operation).
2. Related Background Art
As an example of the conventional communication apparatuses, a facsimile apparatus will be described.
In recent years, there has been developed a facsimile apparatus capable of accommodating a plurality of lines. In such a kind of facsimile apparatus, it is possible to make the facsimile transmission and reception through another line when one usual line is engaged. This type of apparatus is extremely useful in an office where the communication volume is great.
Also, in recent years, it has been required for a facsimile apparatus to provide a lower power dissipation. Particularly, in the overseas market, there is even a movement to enact regulations to control the power dissipation.
In the conventional facsimile apparatus, a system was always in the operational state. The resultant power dissipation was great.
In recent years, however, a facsimile apparatus is arranged to exercise the lower power dissipation. The apparatus is designed to enable the system to be at rest during the period other than the time when it is in transmission and reception or in operation.
Now, in accordance with the conventional art, the description will be made of the low power dissipation facsimile apparatus capable of accommodating only one line as given below.
This kind of facsimile apparatus is structured so as to supply a starting signal to a main power source at the time of facsimile transmission and reception or at the time of operation by an operator.
FIG. 4 is a block diagram which shows an example of such conventional facsimile apparatus as described above.
A main control unit 1a is arranged to control the facsimile apparatus as a whole. A line control unit 2a is to control the line connection.
An operation panel unit 3a comprise a key-board and others that an operator uses to operate the apparatus. A document sheet reading unit 5a contains an image sensor for reading images, and receives electric power form a power source 4a. 
In this facsimile apparatus, a document sheet is read by the image sensor of the scanner 5a when the usual facsimile transmission is performed. Then, the image thus read is compressed by use of the main control unit 1a to send it out to a partner station through the line control unit 2a. The designation of this station is inputted through the operation panel unit 3a. 
Also, for the usual facsimile reception, a call signal (CI signal) is detected from a line. Then, the line control unit 2a connects the line with an apparatus on the partner station to receive the image information transmitted therefrom.
The image thus received is expanded by the main control unit 1a to print it out by a printer control unit 9a on a recording sheet accordingly.
Then, the main control unit 1a controls whether or not the entire system should be in an operation condition or at rest. In this respect, a low power dissipation mode control unit 6a, which is provided for a part of the main control unit 1a, is kept active even when the system is at rest.
The low power dissipation mode control unit 6a monitors the off hooking of a hand set inputted from the line control unit 2a, a CI detection signal, a detection signal of the image sensor inputted from the scanner 5a, and a key input signals inputted from the operation panel unit 3a, respectively, as each of the factors that requires the actuation of the main power source.
Then, each of the circuits that monitors each factor that requires the actuation of the main power source is kept active even when the system is at rest.
The facsimile apparatus is in the low power dissipation mode as being on standby during the period other than the transmission and reception, or the operation. The low power dissipation mode control unit monitors the main power source actuation factors, and actuates the system when either one of the factors is detected.
When the usual operation is possible, the main control unit 1a monitors the main power actuation factors described above, and if any one of the factors is not detected for a predetermined period of time, this unit controls to enable the system itself at rest, and then, transfers the required control to the low power dissipation mode control unit 6a. Thus, the system is allowed to be at rest.
Here, FIG. 5 is a block diagram which shows a example of the conventional facsimile apparatus which is capable of accommodating a plurality of lines.
As shown in FIG. 5, control of a plurality of lines is made possible by installing another main control unit 1b and another line control unit 2b for connection.
As before-mentiones, a conventional facsimile apparatuse can reduce the power dissipation by causing the apparatus to be on standby.
However, the facsimile apparatus capable of accommondating a plurality of lines as described above has circuitry greater than that of such apparatus that deals with only one line, because it is necessary for the former to execute the control of plural lines.
Therefore, even if the control is transferred to the low power dissipation mode, the low power dissipation mode should be implemented with respect to the two main control units 1a and 1b. The resultant power consumption is increased inevitably even when the low power dissipation mode is performed, there is a possibility that the aforesaid power consumption regulation is not satisfied in some foreign countries.
Also, it may be conceivable to devise a method to improve the power source structure in order to serve the purpose. Technically, however, such improvement is extremely difficult.